Selvadurai will still remain on Foursquare's board as an advisor.
He isn't sure of his next steps, but he felt like it was time to
do something new, he wrote in a personal blog post.

His departure comes just before the South By Southwest conference
in Austin later this month, which put Foursquare on the map three
years ago.

He made the formal announcement on his personal blog, though
Om Malik of GigaOm first reported the news. Here's
Foursquare's comment on the news:

When Naveen and Dennis launched foursquare at SXSW 2009, they had a few hundred beta testers.
Now, as we approach our third birthday, we have a community of
over 15 million that has checked in over 1.5 billion times. This
wouldn’t have been possible without Naveen’s creativity, vision,
and tireless work. We’re sad to see him go, but excited to see
what he builds next. We can’t thank him enough for everything
he’s done to make foursquare what it is today.